Why cancer patients experience ‘chemo brain’

Chuck Bednar for redOrbit.com – @BednarChuck

Researchers from the University of British Columbia have for the first time explained why being treated with chemotherapy can adversely affect the cognitive function of cancer patients.

Writing in the journal Clinical Neurophysiology, associate professor Kristin Campbell, former UBC Ph. D. student Julia Kam and their colleagues explained that the phenomenon known as “chemo brain” is marked by excessive mind wandering and an inability to concentrate. While the condition has long been suspected, the reason for it had never been explained.

Campbell explained to redOrbit via email that chemo brain “is a common side effect of cancer treatment where patients report changes in their ability to think, concentrate and remember. It is commonly linked to chemotherapy treatment but the cause is not entirely clear. One idea is that chemotherapy causes low-grade inflammation throughout the body and the inflammatory markers travel in the blood stream and influence the brain structure and function that way.”

“A healthy brain spends some time wandering and some time engaged,” added professor of psychology and co-author Todd Handy. “We found that chemo brain is a chronically wandering brain, they’re essentially stuck in a shut out mode.”

Testing patients for attention level fluctuations

The researchers asked breast cancer survivors to complete a series of tasks as the researchers monitored their brain activity. Nineteen patients who experienced issues related to cognitive function and 12 healthy control subjects completed target-detection tasks.

“The task we used is a very easy computer task that is designed to allow for fluctuations in attention,” Campbell told redOrbit. “Fluctuations in our attention levels is a normal phenomenon and is commonly called ‘mind wandering.’ Since an inability to maintain attention is one of the things patients report with chemo brain, we used this test to see if women who reported chemo brain symptoms were mind wandering more than women who had not had cancer.”

As they took part in those tasks, subjects periodically reported their attentional state, and their brain activity were recorded both during the task and at rest using electroencephalogram (EEG). The researchers found that cancer survivors were less likely to maintain sustained attention during the task, and that their brains displayed greater amounts of neural activity at rest.

Women who were suffering from chemo brain were more likely to stay in a disengaged state, with their minds wandering, Kam and her co-authors wrote. Furthermore, even when survivors believed they were focusing on a task, the EEG measurements indicated that a large portion of their brains were “turned off” and that their minds were wandering.

Searching for ways to test patients for chemo brain

Furthermore, they found evidence suggesting that the cancer survivors were focused more on their “inner world,” and that even when they asked to relax, their brains were more active than the healthy women. Campbell explained that the UBC team’s findings could help health care providers measure the impact of chemotherapy on the brain.

The findings could also provide doctors with a new way to test patients for chemo brain, and to gauge if they are improving over time, she noted, as tests developed for brain injury, Alzheimer’s disease or other cognitive orders have proven ineffective for measuring chemo brain.

“The changes patient report with chemo brain are subtle and the traditional tests used to look at memory and cognitive function may not be sensitive enough to pick up the symptoms,” Campbell told redOrbit. “Our study shows that measuring brain waves (by EEG) during an attention test may be a new way to measure chemo brain symptoms.”

“Identifying a sensitive test is important to allow us to now start to test possible intervention strategies that may help to improve chemo brain. This test will allow us to compare before and after values with a treatment intervention,” she added. “One treatment option we are interested in looking at in the future is to see if exercise may help to improve chemo brain symptoms, [since] exercise has been shown to improve memory and cognitive function in older adults.”

“Chemo brain or cancer-associated cognitive changes, as it is more commonly called in the medical community, is common and does tend to improve over time,” Campbell concluded. “However, for some patients the symptoms do persist. We are interested in finding possible intervention strategies to possibly reduce the severity of the symptoms and assist those who have persistent symptoms more than a year after finishing treatment.”


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